In a CAD environment, the operator uses a combination of keyboard, mouse, and/or tablet to manipulate objects, and a flat screen to display visual feedback. This interface is very effective for 2 Degree-of-Freedom (DoF) drawings such as sections and projections, but has some major limitations for three-dimensional object design and manipulation.
In three-dimensional Cartesian space, position and orientation are defined by three positional coordinates X, Y and Z, and three angular coordinates, pitch, yaw and roll, for a total of 6 DoF. Designing, modeling, and assembling CAD surfaces and solid objects in space using a 2 DoF interface is non-intuitive, time consuming, and requires extensive training. In fact, position is controlled by three variables, but a mouse or tablet allows access to only two variables at a time (i.e. horizontal and vertical position in the plane of the mouse or tablet). Thus, a designer can control only a subset of positional information at any one time. Further, rotation about a given axis requires only one variable for definition. However, there is no rotational input available with the conventional tools. Thus, the designer must translate from a positional mouse displacement to a rotational displacement in order to understand the effect of their input.
A 6 DoF joystick, such as a Spaceball.TM. manufactured by Spaceball Technologies, provides six degrees of freedom. However, the six degrees of freedom do not match position and orientation. Rather, they match the speed at which those parameters are changed. The difference, which may seem subtle, is difficult to cope with and requires extensive training to become proficient.
The same objects modeled with a two-dimensional interface can also be modeled directly in three-dimensions. A virtual reality (VR) environment is one such example. In this case, the object is presented to the designer in a manner which more accurately mimics the presentation of an actual object. The object is placed in the same three-dimensional space as the designer. Thus, the designer would need an interface tool which has 6 DoF allowing position and orientation to be manipulated directly. Such an interface does not exist today.